Help me with these pics please!

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Bryan

Bryan

0
May 31, 2008
29
Tarpon Springs, FL
Recently purchased a house with an inground pool, and the finish is rather unsightly. Can someone tell me what the heck is going on here?? Thanks![attachment=1:fd43xlwr]Pictures 414.jpg[/attachment:fd43xlwr][attachment=0:fd43xlwr]Pictures 415.jpg[/attachment:fd43xlwr]
 

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While I'm no expert on the subject, I would recommend checking out the Pool School link on the top right of the web site here. The Pool Problem area has a wealth of information to get you pointed in the right direction.

Good Luck to you!
 
That's kinda what I was thinking too Richard, just looking for a more definitive initial diagnosis. I'm not a pool newbie, but this is my first IG, so I'm used to vinyl, not plaster/marcite/gunite/whateverthehellelsethereis! I had a TF-100 kit, but it stayed at the last house and I haven't bought a new one yet. I'm in the middle of a partial drain and refill to lower CYA, so as soon as that's done I'll get to work on this problem. I've tried a wire pool brush and it doesn't seem to do anything, so hopefully once I get the CYA down, I can bring the FC up and keep it up for a while, and maybe then the scrubbing will do something.
 
It looks like spot etching, and algae growing in the spots. It is harder to brush because the spots are lower than the rest of the surface. You should use a Stainless steel wire brush to brush and you should shock up to the proper shock level for your cyanuric acid.

If you can provide a full set of test results, than we will have a better idea of what you will need to do to correct this.

FC
CC
pH
TA
Calcium
Cyanuric acid
Borates
Salt
Iron
Copper
Temperature.
 
The low chlorine explains the algae. The negative CSI might have contributed to the spot etching. Spot etching is a controversial issue and there is no definitive cause that is universally accepted.

Maintaining a free chlorine relative to your cyanuric acid will prevent algae in the future. Maintaining a CSI in the 0.0 to +0.3 range will help preserve the integrity of the plaster.
 
JamesW said:
The low chlorine explains the algae. The negative CSI might have contributed to the spot etching. Spot etching is a controversial issue and there is no definitive cause that is universally accepted.

Maintaining a free chlorine relative to your cyanuric acid will prevent algae in the future. Maintaining a CSI in the 0.0 to +0.3 range will help preserve the integrity of the plaster.
Click to expand...

OP's prior CSI apears to be in the -0.2 to -0.3 range (maybe I calced it wrong :scratch) which doesn't seem that far out of range to cause spot etching, if that is what it is? Could you elaborate on what spot etching is exactly and how it is caused? We usually advise folks to maintain a zero to slightly negative CSI to avoid scaling risk, so I'd be interested to understand the suggestion to maintain CSI at zero to +0.3 range. Thanks :goodjob:
 

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257, the spots are concave, and they are slimy, so I'm assuming it's the plaster going away and algae growth on the surface. I hadn't had a test kit til just last week, so I just assumed I was using plenty of chlorine to kill it, but now that I know how high my CYA is, I probably wasn't using near enough. Hopefully with the drain and refill I can get the chlorine up easier and get rid of the ugliness. My bigger concern is the finish; what's causing it and how do I slow it down? Is it just age catching up to it? The pool is 18 years old. As I said before, I've never had an IG, so I have no clue as to the life expectancy of the finish. Thanks!
 
I don't know if I'd call it "spot etching;" it looks more like delaminating plaster to me. It's pretty common in older plaster, and algae does tend to preferentially grow in the concave spots. You can get the pool clean and keep it clean with sufficient chlorine, but a replaster job is near on the horizon.
 
I'm pretty sure that it is spot etching. It looks like the classic presentation to me, and I have seen it many times. If you look at the second picture between the tile and water, you can see the spots more clearly.

I have also seen many delaminations. Delaminations are typically deeper holes where an entire layer of plaster has broken off. It does not look like delaminations to me.

Bryan, I think that the best thing to do to protect the plaster is keep the pH in the 7.7 to 7.9 range and the CSI in the 0.0 to +0.3 range. Brush periodically with a nylon bristle brush and maintain a chlorine level sufficient for your cyanuric acid level.

If there are any delaminations, then there is not much you can do about them other than to avoid direct sun on them, as this causes delaminations to grow. Direct sun means without water. Direct sun without water causes the delaminated sections to heat up and expand. If delaminations are kept underwater then they can still expand, but usually at a much slower pace.
 
Yeah, I don't see any chunks of plaster missing, just a lot of areas that look like they've been eaten away. I replaced what I think was about 15-20% of the water to bring the CYA and CH down, and shocked the pool tonight. Now if only I didn't have that pesky thing known as "work" to go to tomorrow morning. Hopefully the FC will stay up til I get home tomorrow night, and I'll start on the brushing. Not looking forward to that part for sure. I'll pick up some baking soda on the way home too, as I'm sure the pH and TA will be low after the water swap.

In playing around with Pool Calc, it looks like if I keep pH around 7.8, TA around 90, CH around 350, and CYA around 70, then CSI should stay between 0 and .3, which will give me slower plaster deterioration but a slightly higher possibility of scaling, correct? If so, I like that thought process, as I'm not financially ready to refinish the pool just yet. I mean, heck, I'd like to get a season or two out of it since I just bought the place!

Thanks for everyone's help and advice so far!

Bryan
 
As long as you keep the CSI between 0.0 and +0.3, then you should not get any scaling. You should clean the tile weekly using a nylon scrubbing pad, such as the green Scotch Brite pads. You should brush the pool weekly with a nylon bristle brush.

When using the pool calculator to calculate your CSI you want to calculate it for your current temperature and for the highest temperature the water will get to. This will help you plan how you want to adjust the chemistry as the water warms up. Warmer water increases the CSI, so you need to make sure that you have something you can lower to compensate. pH and TA are the easiest to lower, while calcium is more difficult.

While the water is cold, you could target a CSI of close to 0.0 and that will give you some room (about 0.3 CSI points) as the water warms up.

You should have the water tested for iron and copper just to make sure that there won't be any issues with metal staining.

Spot etching is not all that uncommon. It is probably due to defects in the plaster materials or application. Aggressive water probably increases the speed of the etching (or leaching).

With good maintenance, you should be able to get several more years out of the plaster.
 
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